A Study On Quantitative Soil Erosion Assessment And Soil And Water Conservation Planning In A Small Watershed

Quantitative evaluation of land resources and soil erosion, and soil conservation planning, were studied systematically supported by GIS with digital map, remote sensing imagery, field survey data, according to needs of soil and water conservation, and eco-environmental rehabilitation in small watershed, on basis of theories of landscape-ecology, land resource science, soil erosion and soil and water conservation science.iapproaches on multi-source data integration and multi-items database establishment were discussed, including basic polygon used to assess soil erosion and soil/water conservation planning, organization of data layers and data items, data integration, data file management and metadata standard.iiaccording to characteristics of soil and water conservation and eco-environmental rehabilitation, the concept about land for eco-protection was introduced. Land suitability and its potential of developing commodity agro-production in the hilly-gully region were analyzed. The results show that land for eco-protection is prerequisite, and area of land for commodity agro-products is limited; 2) commodity agro-production model in the hilly-gully region is a commodity production with limited regional scope under well-protected eco-system.iiiintegrating hullslope soil erosion prediction model with GIS, methods of upscaling from slope segment to a small watershed, spatio-temporal analyzing on soil loss differentiation were proposed. The results show that 1) maximum soil loss in Zifanggou watershed is about 50,000Ikm2.a, average soil erosion modular decreases per year by 5% from 1958 to 1999. The area of slightlsevere soil erosion decreases/increases obviously, however, the area of medium erosion does not obviously change. 2) Under irrational landuse and shortage of necessary soil and water conservation measures, soil erosion mainly occurred at hullslopes; otherwise mainly occurred at gully-slopes.ivspatio-temporal characteristics of landuse and soil erosion, and methodology of soil and water conservation planning in a small watershed were studied. The results show that 1) landuse severely changed in the transmit regions among hilly-gully region, second forest region of the south part and dryland farming area in the middle-north part, where was core places for soil and water conservation, eco-environmental rehabilitation; 2) the area along gully edge ( near 15 to 30 m to gully edge), and sloping farmland with about 25 slope degree in small watersheds are susceptible belts of soil erosion and landuse change, are also core places for soil and water conservation; 3) After soil and water conservation planning was implemented, average soil loss in the watershed may decrease to 938 to21725t/km .a, which is nearly equal to soil loss tolerance value.